linux-kernel - Re: [PATCH v4 6/9] usb: dwc3: Rework resets initialization to be more flexible

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Message-ID: <87k18mhaiq.fsf@gmail.com>
Date:   Wed, 30 Oct 2019 11:01:49 +0200
From:   Felipe Balbi <balbi@...nel.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     lkml <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        ShuFan Lee <shufan_lee@...htek.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Yu Chen <chenyu56@...wei.com>,
        Hans de Goede <hdegoede@...hat.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Jun Li <lijun.kernel@...il.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Jack Pham <jackp@...eaurora.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        "open list\:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v4 6/9] usb: dwc3: Rework resets initialization to be more flexible


Hi,

John Stultz <john.stultz@...aro.org> writes:

> On Tue, Oct 29, 2019 at 2:17 AM Felipe Balbi <balbi@...nel.org> wrote:
>> John Stultz <john.stultz@...aro.org> writes:
>> > The dwc3 core binding specifies one reset.
>> >
>> > However some variants of the hardware my not have more.
>>                                         ^^
>>                                         may
>>
>> According to synopsys databook, there's a single *input* reset signal on
>> this IP. What is this extra reset you have?
>>
>> Is this, perhaps, specific to your glue layer around the synopsys ip?
>
> Likely (again, I unfortunately don't have a ton of detail on the hardware).
>
>> Should, perhaps, your extra reset be managed by the glue layer?
>
> So yes the dwc3-of-simple does much of this already (it handles
> multiple resets, and variable clocks), but unfortunately we seem to
> need new bindings for each device added?  I think the suggestion from
> Rob was due to the sprawl of bindings for the glue code, and the extra
> complexity of the parent node.  So I believe Rob just thought it made
> sense to collapse this down into the core?
>
> I'm not really passionate about either approach, and am happy to
> rework (as long as there is eventual progress :).
> Just let me know what you'd prefer.

Well, I was under the impression we were supposed to describe the
HW. Synopsys IP has a single reset input :-p

-- 
balbi